In a vacuum cleaner a primary source of noise is the exhaust air flow. A goal of vacuum cleaner manufacturers is to minimize the exhaust air flow noise to reduce as much as possible the annoyance to the vacuum cleaner operator.
Vacuum cleaner manufactures have taken different approaches to constructing noise reduction systems. These noise reduction systems have been utilized in both conventional and up right vacuum cleaners. One approach is taught in U.S. Pat. No. 2,340,437 to Stoner and in U.S. Pat. No. 4,617,034 to Ikezaki et al., which each disclose a vacuum leaner having a resonant muffler formed within the cleaner. These resonant chambers are designed to attenuate the sound waves over a certain range of frequency.
An alternative approach to reducing noise may be seen in U.S. Pat. No. 3,218,783 to Ripple and U.S. Pat. No. 4,446,594 to Watanabe et al., which disclose the use of sound absorbing material lining the exhaust passageway as a means of reducing exhaust noise.
U.S. Pat. No. 4,970,753 to Herron, Jr. assigned to Ryobi Motor Products Corp., discloses a cartridge which is provided for selective installation within the vacuum cleaner. Exhaust air flows through the cartridge which is configured to interfere with the free flow of the exhaust. The cartridge is a two-part unit wherein each part includes an array of parallel baffle plates which are interleaved with the array of baffle plates of the other part juxtaposed to the baffle plates of the opposing part to form a complete air flow baffle cartridge. The baffle plates for a labyrinth causing the air to undergo a plurality of changes of direction prior to leaving the vacuum cleaner, thereby reducing energy from the air flow.
The present invention is directed to improving know noise-reduction systems for use in upright vacuum cleaners.